Agricultural harvesting heads such as draper platforms are designed to follow closely along the ground harvesting crops. To ensure that they follow the ground closely, they are configured to contact the ground and apply a slight ground force to the ground. Hydraulic electric circuits are typically provided to ensure that only a small portion of their weight is actually pressed against the ground. As the ground rises and falls underneath the agricultural harvesting head, the position of the agricultural harvesting head is adjusted up and down with respect to the agricultural combine on which the agricultural harvesting head is supported. This permits the agricultural harvesting head to adjust to changing terrain.
In recent years, articulated agricultural harvesting heads have been designed. Articulated heads comprise two or more elongated sections that are hinged to each other. As the terrain changes, each section rises and falls with respect to the ground independently of the other sections.
One problem in articulated agricultural harvesting heads is maintaining a relatively constant and light force against the ground. In a three section articulated agricultural harvesting head, for example, the two end sections are hingeably connected to a center section. The center section is supported on the agricultural combine itself. The two outer hinged sections are supported on the ground, and also are supported on the center section itself. To maintain a constant ground force of the two outer hinged sections against the ground, some of their load must be transferred to the center section. Yet the center section must also be maintained at a relatively constant ground force against the ground. This transfer of loads between the sections and to the agricultural combine itself is difficult.
In CA 2,665,589 A1, the outer hinged sections of the agricultural harvesting head are supported on wheels. As the terrain changes, the terrain pushes against the wheels, which in turn raises and lowers the outer hinged sections with respect to the center section. One drawback to this arrangement is the increase in weight due to the wheels required to support the wing sections.
In US 2003/074876 A1, an arrangement of linkages, levers, and springs are used to couple the outer sections of the agricultural harvesting head to the central section. One drawback to this arrangement is the added weight and complexity of the linkages, levers, and springs.
The Geringhoff company has a draper called “Triflex” that uses an accumulator (a hydraulic spring) to control the downforce applied to the ground.
What is needed, therefore, is an improved arrangement for supporting the outer sections of an articulated agricultural harvesting head and controlling their ground force.
It is an object of this invention to provide such an arrangement.